Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: AirForcePOL on November 26, 2013, 01:17:33 PM
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My Hardy H2 has been burning a lot more wood than normal lately. A load that used to last me 12-16 hours has only been lasting about 8. I haven't changed anything in my system since I hooked it up 3 years ago.
The only thing that I can think that has happened is that when I was one vacation a few weeks ago my brother was taking care of the stove and accidentally left the ash door open on the day that I got home. The stove boiled over and lost quite a bit of water. This caused the water level to drop below the pump and the pump continued to run without any water in the lines. Surely if there was damage to the pump it wouldn't effect burn times, right? Or I was thinking that maybe the aquastat got too hot and it caused damage to it and it isn't controlling the temp correctly now?
I have cheap homemade pipe that has done pretty good for me and I haven't had any problems with it. I bought a infrared thermometer today and I'm going to see how much heat loss I have between the stove and the house.
Does anyone have any suggestions on what to check other than those things? My firerope is in good shape and seals up pretty good around the ash door and firebox door. I just don't see what could have caused the sudden change in efficiency. Any ideas would be appreciated! Thanks!
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I'm guessing your pump isn't performing up to snuff. From what I've read it doesn't take long to ruin one if you run them dry.
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My Hardy H2 has been burning a lot more wood than normal lately. A load that used to last me 12-16 hours has only been lasting about 8. I haven't changed anything in my system since I hooked it up 3 years ago.
The only thing that I can think that has happened is that when I was one vacation a few weeks ago my brother was taking care of the stove and accidentally left the ash door open on the day that I got home. The stove boiled over and lost quite a bit of water. This caused the water level to drop below the pump and the pump continued to run without any water in the lines. Surely if there was damage to the pump it wouldn't effect burn times, right? Or I was thinking that maybe the aquastat got too hot and it caused damage to it and it isn't controlling the temp correctly now?
I have cheap homemade pipe that has done pretty good for me and I haven't had any problems with it. I bought a infrared thermometer today and I'm going to see how much heat loss I have between the stove and the house.
Does anyone have any suggestions on what to check other than those things? My firerope is in good shape and seals up pretty good around the ash door and firebox door. I just don't see what could have caused the sudden change in efficiency. Any ideas would be appreciated! Thanks!
This is some old school thinking what kinda lines do you have in the trench ? water touching hot lines in trench can make your stove never heat up . I seen how this works when it happens . I melded and bent that thick cast iron grate in the bottom of my heatmor . happened when I first installed Mine in 1996. Its something to look in to . I'm in super heavy clay you make a hole you make a pond .
This might not be it . but wow its all stuck in my mind :bash:
heat550
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It seems to heat the house fine though but it just seems like it takes a while to get up to temp. It's very possible that the pump isn't performing well though.
The lines I have are just insulated pex inside of corrugated pipe. I just don't see how water would get in there unless it cracked somewhere. I haven't had a problem until now. I will test the heat loss when I get home to see what I'm losing.
thanks guys!
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Some other possibilities would be a drop in outdoor temperature or lesser quality/wet/ softer wood. I'm thinking an air leak due to damaged seal or partially open air supply would permit extra burning but would show up as higher than normal operating temperature at the boiler.(would likely overheat)
Somebody please correct me if I'm wrong, if your pump is not circulating water then no heat is carried away from the boiler so wood consumption goes down and house gets cold. Your infrared thermometer should indicate if your buried line is o.k., hopefully you find an easy fix.
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I agree with idahohay - I say it is NOT the pump. If the pump was damaged, it would NOT pump as much water which would make the wood last much longer!
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But if he's lost gpm's due to a damaged pump wouldn't the furnace blower be drawing more heat out of the slower moving water thus making his burner cycle more often to maintain temp thus burning more wood????
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Get the temp if the water leaving the stove, temp before and after the hx and temp when it gets back to the stove. I am betting your pump is cooked and pumping water very slowly through your hx causing a huge temp drop.
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regaurdless of how fast the water is moving (as long as it is fast enough to provide the needed btu per hour) if it was pumping 6 gpm or 3 gpm the hosue wold ned the same amount of btu if pumping 6 gpm the return temp might be twice as high as it it was pumping 3 gpm but it would have drawn twice the water from the OWB so lets say the house required 100 btu and in 6gpm the house would satisfied in 10 min, that would mean at 3 gpm the house would be satisfied in 20 min...the same amount of water and the same amount of btu so the OWB would be the same temp
there are only 4 reasons to burn more wood....1 is the heat load has increased due to outside temps or changes to your insulation ect. 2...you have a heat leak (or draw) between the owb and the home (such as water logged pipes) or 3...the wood you are now burning is not as heavy as you were burning so you need more wood to equal the same weight as what you were burning (as btu in a pound of wood are the same no matter what type of wood) and 4...your OWB is malfunctioning
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Not a pump issue, if it were his burn times would be extended not reduced .. If less heat is being pulled from stove it would last longer
Doubting its air, air the hx would make the heat exchanger pull less heat
His lines may be the issue
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Thanks for all of the replies guys. When I got home I tried checking the temps with the gun but that didn't work too good. I could get a good reading inside right before my hx but not at the boiler. I think it has something to do with the outside temps because it was only reading around 120 degrees at the boiler. My aquastat was set at 160 and it was reading around 153 inside. That was with the stove sitting idle.
I'm starting to think maybe it's the wood I'm burning. I'm going to go get a load of some stuff I cut a while back and try that out. The fire just doesn't seem to burn as good as it usually does.
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yes i should have added wet wood vrs dry wood in there as well..if you are burning wet wood it can take almost all the btu value in that wood to dry the wood enough to burn it
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Willie is dead on. Wood produces btu's and that heat has to go somewhere. If the fire is producing it it will go into the water and then at some point it has to be transferred into the air. You can come up with theories on pumps and heat exchanges but if that was true he would be getting more heat into the house and overheating his home.
I've had customers in the past completely convinced that they were burning too much wood because the thermostat on the stove was malfunctioning. I always ask if the furnace is boiling over, of course the answer is always no. So then I ask where the extra heat is going? You can't produce heat and have it simply disappear, its has to go somewhere.
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Well I switched up my wood and I got 13 hours on a load last night with 15 degree temps. I think that was the problem! Thanks again!
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AirForcePOL, You mentioned having problems with your infrared thermometer. I bought a cheao Harbor Freight and noticed problems when trying to read pipe temps. The laser dot is pretty far off on mine and had best results reading pipe holding it very close and slowly moving it across the target until reads the highest. When using it in the pump area at the back of my boiler I found that backing the targeted area with a wood scrap helped. When i would just shoot it at the piping, I'm sure it was hit or miss, sometimes reading the tank or firebox surface.
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AirForcePOL, You mentioned having problems with your infrared thermometer. I bought a cheao Harbor Freight and noticed problems when trying to read pipe temps. The laser dot is pretty far off on mine and had best results reading pipe holding it very close and slowly moving it across the target until reads the highest. When using it in the pump area at the back of my boiler I found that backing the targeted area with a wood scrap helped. When i would just shoot it at the piping, I'm sure it was hit or miss, sometimes reading the tank or firebox surface.
Thanks for the tips! I have the cheap harbor freight one as well. I tried putting duct tape on the pipe like the manual said but that didn't work too good.